On Monday 03 December 2007 22:26:28 Nick Piggin wrote:
> There is one slight downside -- direct block device access and filesystem
> metadata access goes through an extra copy and gets stored in RAM twice.
> However, this downside is only slight, because the real buffercache of the
> device is now reclaimable (because we're not playing crazy games with it),
> so under memory intensive situations, footprint should effectively be the
> same -- maybe even a slight advantage to the new driver because it can also
> reclaim buffer heads.
For the embedded world, initramfs has pretty much rendered initrd obsolete,
and that was the biggest user of the ramdisk code I know of. Beyond that,
loopback mounts give you more flexible transient block devices than ramdisks
do. (In fact, ramdisks are such an amazing pain to use/size/free that if I
really needed something like that I'd just make a loopback mount in a ramfs
instance.)
Embedded users who still want a block interface for memory are generally
trying to use a cramfs or squashfs image out of ROM or flash, although there
are flash-specific filesystems for this and I dunno if they're actually
mounting /dev/mem at an offset or something (md? losetup -o? Beats me, I
haven't tried that myself yet...)
Rob
--
"One of my most productive days was throwing away 1000 lines of code."
- Ken Thompson.
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